This invention relates to tuning apparatus and, more particularly, to such tuning apparatus which is capable of being tuned over plural broadcast frequencies, such as AM and FM frequencies, and in which the tuning apparatus automatically is switched from one to another frequency band in response to the selection of a desired frequency.
Radio receiving apparatus is commercially available wherein the radio receiver can be tuned to a desired frequency in any one of plural broadcast frequency bands. For example, a so-called AM/FM radio receiver is provided with an AM tuner and with an FM tuner. Either one or the other of the AM and FM tuners can be operated to select a desired broadcast frequency either in the AM frequency band or in the FM frequency band.
In a typical AM/FM radio receiver, a dial scale is provied with two sets of calibrated gradations. One set of gradations represents the AM frequencies which can be received; and the other set of gradations represents the FM frequencies which can be received. In general, the AM frequency gradations and the FM frequency gradations are represented in respective linear arrays. An indicator, such as a dial needle, is moved in correspondence with the tuning of the AM or FM tuners. A single indicator may be provided so as to simultaneously scan the AM and the FM frequency gradations during a tuning operation.
Usually, a frequency band selection switch must be operated in addition to a tuning knob so that the user will be provided with an indication of the particular AM or FM frequency to which the radio receiver is tuned. Thus, if the radio receiver is tuned to a particular AM frequency, and if the user then wishes to tune the radio receiver to a desired FM frequency, the tuning knob must be operated to dispose the indicator at the desired FM frequency gradation and, in addition, the frequency band selection switch must be operated to switch from the AM tuner to the FM tuner. If the radio receiver then is to be tuned to another desired AM frequency, the foregoing operation must be repeated wherein the tuning knob is adjusted to position the indicator at the desired AM frequency gradation and the frequency band selection switch also must be operated to change from FM band selection to AM band selection. Accordingly, this two-step operation, i.e., tuning knob adjustment and frequency band selection, may be troublesome to the user. Typically, when the user wishes to receive a broadcast frequency from a different frequency band, he often forgets to operate the frequency band selection switch.